Using embryos of the free-living soil nematode Caenorhabditis elegans as a model, we plan to study the localization of specific proteins, in particular cell-surface molecules and cytoplasmic ribonucleoprotein components, during oogenesis and early embryogenesis. 1) Mouse monoclonal antibodies, elicited against these antigens and produced using the hybridoma technique will be used with fluorescent labeled heterologous anti-mouse-immunoglobulin to locate target macromolecules in situ by fluorescence microscopy of antibody-treated whole embryo, oocyte, and gonad preparations. 2) If antibodies specific for various subsets of the ribonucleoprotein particle (RNP) population are obtained, such antibodies will be used to locate these subsets in situ, as well as to isolate these subsets and determine whether they contain unique subsets of the mRNA population by hybridization to an already characterized library of cloned C. elegans DNA sequences. 3) A set of maternal-effect embryonic-lethal mutants that cause early cleavage abnormalities (Wood et al., Dev. Biol. 74, 446-469, 1980) will be examined for effects on localization of specific embryonic components. These investigations should provide approaches to the important unanswered questions of how cytoplasmic determinants are partitioned during asymmetric cleavages in development, whether these components include cell surface molecules and specific mRNA sequences, and whether the behavior of specific mRNA sequences may be correlated with the protein compositions of the RNP particles that contain them.